Double-ended ceramic discharge lamps, i.e. lamps in which the electrodes enter the ceramic discharge vessel from opposite sides, are well known. For example, U.S. Pat. No. 5,721,465 describes a xenon arc lamp with a cylindrical ceramic body into which an elliptical reflector is molded and a quartz window is mounted opposite the reflector. The lamp has opposed electrodes: one which extends into the discharge vessel from the base of the reflector, the other from the opposite side where the window is located, i.e., the light-emitting end. Similar configurations are found in U.S. Pat. Nos. 6,200,005, 6,285,131, 6,351,058, 6,597,087, 6,602,104 and 6,316,867. However, a common disadvantage with these lamps is that the window-side electrode and its mounting structure obstruct a portion of the light exiting the window.
Also known are singled-end ceramic discharge lamps, i.e., lamps in which the electrodes enter the discharge vessel from the same side. For example, European Patent Application No. EP 1 111 654 A1 describes several single-ended configurations. Although one embodiment is shown with an integral lens in the dome to enhance light intensity distribution, the discharge vessels do not otherwise attempt to focus the arc as in the above-described double-ended lamps. Examples of other single-ended lamps are shown in U.S. Patent Publication Nos. 2005/0211370 and 2005/0212433 which describe different electrode/capillary configurations but also do not provide a means for focusing the arc.